:root {
  --bg: #0d1117;
  --bg-raised: #161b22;
  --bg-sunken: #010409;
  --bg-input: #0a0e14;
  --border: #30363d;
  --border-soft: #21262d;
  --fg: #e6edf3;
  --fg-dim: #8b949e;
  --fg-dimmer: #6e7681;
  --accent: #e3b341;
  --accent-fg: #1c1206;
  --red: #ff7b72;
  --green: #3fb950;
  --mono: "Menlo", "Monaco", "Cascadia Code", "Consolas", "Liberation Mono", monospace;
  --ui: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;

  --g0: #58a6ff;
  --g1: #3fb950;
  --g2: #d2a8ff;
  --g3: #ffa657;
  --g4: #f778ba;
  --g5: #39c5cf;
  --g6: #e3b341;
  --g7: #ff7b72;
}

* ,
*::before,
*::after {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  min-height: 100%;
  background: var(--bg);
  color: var(--fg);
}

body {
  font-family: var(--ui);
  font-size: 14px;
  line-height: 1.5;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  -webkit-font-smoothing: antialiased;
}

code {
  font-family: var(--mono);
  background: var(--bg-sunken);
  border: 1px solid var(--border-soft);
  border-radius: 4px;
  padding: 0 4px;
  font-size: 0.92em;
  color: var(--fg);
}

button,
input,
select,
textarea {
  font-family: inherit;
  color: inherit;
}

:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ── top bar ── */
.topbar {
  border-bottom: 1px solid var(--border);
  background: var(--bg-raised);
  padding: 16px 22px;
  flex-shrink: 0;
}

.brand {
  font-family: var(--mono);
  font-size: 18px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.tag {
  color: var(--fg-dim);
  font-size: 13px;
  margin-top: 3px;
}

/* ── layout ── */
.layout {
  flex: 1;
  padding: 18px 22px 32px;
  max-width: 1320px;
  width: 100%;
  margin: 0 auto;
}

.columns {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: 20px;
  margin-top: 20px;
}

@media (max-width: 900px) {
  .columns {
    grid-template-columns: 1fr;
  }
}

.col {
  min-width: 0;
}

.panel-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px;
  margin: 18px 0 8px;
}

.panel-head:first-child {
  margin-top: 0;
}

.panel-head h2 {
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-dim);
  margin: 0;
  font-weight: 700;
}

.panel-head h3 {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-dimmer);
  margin: 10px 0 6px;
  font-weight: 700;
}

.hint {
  font-size: 11.5px;
  color: var(--fg-dimmer);
}

/* ── pattern bar ── */
.pattern-bar {
  background: var(--bg-raised);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 14px;
}

.pattern-row {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.slash {
  font-family: var(--mono);
  color: var(--fg-dimmer);
  font-size: 17px;
  user-select: none;
}

.pattern-input {
  flex: 1 1 260px;
  min-width: 160px;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--fg);
  font-family: var(--mono);
  font-size: 15px;
  padding: 8px 10px;
}

.pattern-input:focus {
  border-color: var(--accent);
}

.flags {
  display: flex;
  gap: 4px;
}

.flag {
  position: relative;
  display: inline-flex;
  cursor: pointer;
}

.flag input {
  position: absolute;
  opacity: 0;
  width: 100%;
  height: 100%;
  margin: 0;
  cursor: pointer;
}

.flag span {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 26px;
  height: 30px;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--bg-input);
  color: var(--fg-dimmer);
  font-family: var(--mono);
  font-size: 13px;
  font-weight: 700;
  transition: background 0.1s, color 0.1s, border-color 0.1s;
}

.flag input:checked + span {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-fg);
}

.flag input:focus-visible + span {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.flag:hover span {
  border-color: var(--fg-dimmer);
}

.preset-select {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 7px 8px;
  font-size: 12.5px;
}

.btn {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--fg);
  font-size: 12.5px;
  padding: 7px 11px;
  cursor: pointer;
  transition: border-color 0.1s, background 0.1s;
}

.btn:hover {
  border-color: var(--fg-dimmer);
  background: var(--bg-sunken);
}

.btn:active {
  transform: translateY(1px);
}

.pattern-status {
  min-height: 0;
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--fg-dimmer);
}

.pattern-status.error {
  color: var(--red);
  margin-top: 6px;
  padding: 6px 8px;
  background: rgba(255, 123, 114, 0.08);
  border: 1px solid rgba(255, 123, 114, 0.3);
  border-radius: 6px;
}

.pattern-highlight {
  margin-top: 8px;
  font-family: var(--mono);
  font-size: 13.5px;
  padding: 8px 10px;
  background: var(--bg-sunken);
  border: 1px solid var(--border-soft);
  border-radius: 6px;
  white-space: pre-wrap;
  word-break: break-all;
  min-height: 1.6em;
}

.placeholder {
  color: var(--fg-dimmer);
  font-style: italic;
}

/* pattern token colors */
.tok-plain {
  color: var(--fg);
}
.tok-literal {
  color: var(--fg);
}
.tok-dot {
  color: var(--g6);
  font-weight: 700;
}
.tok-anchor {
  color: var(--g3);
  font-weight: 700;
}
.tok-escape {
  color: var(--g0);
}
.tok-backref {
  color: var(--g4);
  font-weight: 700;
}
.tok-class {
  color: var(--g5);
  background: rgba(57, 197, 207, 0.1);
  border-radius: 3px;
}
.tok-alt {
  color: var(--red);
  font-weight: 700;
}
.tok-quant {
  color: var(--accent);
  font-weight: 700;
}
.tok-group-marker,
.tok-paren {
  font-weight: 700;
}
.tok-depth-0 {
  color: var(--g0);
}
.tok-depth-1 {
  color: var(--g1);
}
.tok-depth-2 {
  color: var(--g2);
}
.tok-depth-3 {
  color: var(--g3);
}

/* ── test string ── */
.test-input {
  width: 100%;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--fg);
  font-family: var(--mono);
  font-size: 13.5px;
  padding: 10px;
  resize: vertical;
}

.test-input:focus {
  border-color: var(--accent);
}

.match-summary {
  font-size: 12px;
  color: var(--fg-dim);
  font-family: var(--mono);
}

.test-highlight {
  font-family: var(--mono);
  font-size: 13.5px;
  background: var(--bg-sunken);
  border: 1px solid var(--border-soft);
  border-radius: 6px;
  padding: 10px;
  white-space: pre-wrap;
  word-break: break-word;
  min-height: 2.4em;
}

.m-match {
  background: rgba(227, 179, 65, 0.16);
  border-radius: 3px;
  box-shadow: inset 0 -1px 0 0 rgba(227, 179, 65, 0.6);
}

.m-match:empty::after {
  content: "\2038";
  color: var(--accent);
}

.m-group {
  border-radius: 2px;
  padding-bottom: 1px;
}
.g0 {
  box-shadow: inset 0 -2px 0 0 var(--g0);
}
.g1 {
  box-shadow: inset 0 -2px 0 0 var(--g1);
}
.g2 {
  box-shadow: inset 0 -2px 0 0 var(--g2);
}
.g3 {
  box-shadow: inset 0 -2px 0 0 var(--g3);
}
.g4 {
  box-shadow: inset 0 -2px 0 0 var(--g4);
}
.g5 {
  box-shadow: inset 0 -2px 0 0 var(--g5);
}
.g6 {
  box-shadow: inset 0 -2px 0 0 var(--g6);
}
.g7 {
  box-shadow: inset 0 -2px 0 0 var(--g7);
}

.dot {
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  margin-right: 5px;
  flex-shrink: 0;
}
.dot.m-dot {
  background: var(--accent);
}
.dot.g0 {
  background: var(--g0);
  box-shadow: none;
}
.dot.g1 {
  background: var(--g1);
  box-shadow: none;
}
.dot.g2 {
  background: var(--g2);
  box-shadow: none;
}
.dot.g3 {
  background: var(--g3);
  box-shadow: none;
}
.dot.g4 {
  background: var(--g4);
  box-shadow: none;
}
.dot.g5 {
  background: var(--g5);
  box-shadow: none;
}
.dot.g6 {
  background: var(--g6);
  box-shadow: none;
}
.dot.g7 {
  background: var(--g7);
  box-shadow: none;
}

/* ── match list ── */
.match-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.match-card {
  background: var(--bg-raised);
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  padding: 9px 11px;
}

.match-card-head {
  display: flex;
  align-items: center;
  font-family: var(--mono);
  font-size: 12.5px;
  font-weight: 700;
  color: var(--fg-dim);
}

.match-card-head .range {
  margin-left: 6px;
  font-weight: 400;
  color: var(--fg-dimmer);
}

.match-text {
  font-family: var(--mono);
  font-size: 13.5px;
  margin: 5px 0 0 13px;
  word-break: break-word;
}

.groups {
  margin: 6px 0 0 13px;
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.group-row {
  display: flex;
  align-items: center;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--fg-dim);
}

.unmatched {
  color: var(--fg-dimmer);
  font-style: italic;
}

.empty {
  color: var(--fg-dimmer);
  font-size: 13px;
  font-style: italic;
  margin: 0;
}

.empty.error {
  color: var(--red);
  font-style: normal;
}

/* ── replace ── */
.replace-panel {
  margin-top: 16px;
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  background: var(--bg-raised);
  padding: 4px 12px 12px;
}

.replace-panel summary {
  cursor: pointer;
  padding: 8px 0;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-dim);
  font-weight: 700;
  user-select: none;
}

.replace-panel summary:hover {
  color: var(--fg);
}

.replace-label {
  display: block;
  font-size: 12px;
  color: var(--fg-dim);
  margin-bottom: 6px;
}

.replace-input {
  width: 100%;
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 10px;
  font-family: var(--mono);
  font-size: 13.5px;
}

.replace-input:focus {
  border-color: var(--accent);
}

.replace-output {
  font-family: var(--mono);
  font-size: 13px;
  background: var(--bg-sunken);
  border: 1px solid var(--border-soft);
  border-radius: 6px;
  padding: 9px 10px;
  white-space: pre-wrap;
  word-break: break-word;
  margin: 0;
  max-height: 220px;
  overflow: auto;
}

/* ── explain column ── */
.flags-glossary {
  font-size: 13px;
}

.flag-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.flag-list li {
  color: var(--fg-dim);
}

.outline-wrap {
  background: var(--bg-raised);
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  padding: 10px 14px;
  max-height: 460px;
  overflow: auto;
}

ul.outline {
  list-style: none;
  margin: 0;
  padding-left: 16px;
  border-left: 2px solid var(--border-soft);
}

ul.outline:first-child {
  padding-left: 0;
  border-left: none;
}

ul.outline li {
  margin: 8px 0;
}

.outline-head {
  font-size: 13px;
  line-height: 1.5;
}

.outline-head strong {
  color: var(--accent);
  font-weight: 700;
}

.outline-head em {
  color: var(--red);
  font-style: normal;
}

/* ── cheatsheet ── */
.cheatsheet {
  margin-top: 16px;
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  background: var(--bg-raised);
  padding: 4px 12px 12px;
}

.cheatsheet summary {
  cursor: pointer;
  padding: 8px 0;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-dim);
  font-weight: 700;
  user-select: none;
}

.cheatsheet summary:hover {
  color: var(--fg);
}

.cheatsheet-body {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}

@media (max-width: 560px) {
  .cheatsheet-body {
    grid-template-columns: 1fr;
  }
}

.cheat-group h4 {
  margin: 0 0 6px;
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--fg-dimmer);
}

.cheat-row {
  display: flex;
  align-items: baseline;
  gap: 8px;
  font-size: 12px;
  color: var(--fg-dim);
  padding: 2px 0;
}

.cheat-row code {
  flex-shrink: 0;
  min-width: 64px;
  text-align: center;
}

/* ── field exercises ── */
.exercises-panel {
  margin-top: 20px;
  border: 1px solid var(--border-soft);
  border-radius: 10px;
  background: var(--bg-raised);
  padding: 4px 16px 16px;
}

.exercises-panel summary {
  cursor: pointer;
  padding: 10px 0;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--fg-dim);
  font-weight: 700;
  user-select: none;
}

.exercises-panel summary:hover {
  color: var(--fg);
}

.exercises-intro {
  margin: 0 0 14px;
  font-size: 12.5px;
  color: var(--fg-dim);
  max-width: 780px;
}

.exercises-intro strong {
  color: var(--fg);
  font-weight: 700;
}

.exercise-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 14px;
}

.exercise-card {
  background: var(--bg-sunken);
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  padding: 12px 13px;
}

.exercise-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}

.exercise-title {
  font-family: var(--mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--fg);
}

.exercise-status {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--fg-dimmer);
  white-space: nowrap;
}

.exercise-status.ok {
  color: var(--green);
}

.exercise-status.bad {
  color: var(--red);
}

.exercise-prompt {
  font-size: 12.5px;
  color: var(--fg-dim);
  margin: 6px 0 10px;
}

.exercise-input-row {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.exercise-input-row .slash {
  font-size: 14px;
}

.exercise-pattern-input,
.exercise-flags-input {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--fg);
  font-family: var(--mono);
  font-size: 12.5px;
  padding: 6px 8px;
}

.exercise-pattern-input {
  flex: 1 1 140px;
  min-width: 100px;
}

.exercise-pattern-input:focus,
.exercise-flags-input:focus {
  border-color: var(--accent);
}

.exercise-flags-input {
  width: 52px;
  flex: 0 0 auto;
}

.exercise-hint-btn,
.exercise-reveal-btn {
  padding: 6px 9px;
  font-size: 11px;
}

.exercise-hint {
  margin: 8px 0 0;
  font-size: 12px;
  color: var(--accent);
  font-style: italic;
}

.exercise-cases {
  margin-top: 10px;
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.exercise-case {
  display: flex;
  align-items: baseline;
  gap: 6px;
  font-size: 11.5px;
  color: var(--fg-dimmer);
}

.exercise-case-icon {
  font-family: var(--mono);
  width: 12px;
  flex-shrink: 0;
  text-align: center;
}

.exercise-case.ok .exercise-case-icon {
  color: var(--green);
}

.exercise-case.bad .exercise-case-icon {
  color: var(--red);
}

.exercise-case-kind {
  flex-shrink: 0;
  min-width: 96px;
  color: var(--fg-dimmer);
}

.exercise-case code {
  color: var(--fg-dim);
  word-break: break-word;
}

/* ── footer ── */
.footer {
  border-top: 1px solid var(--border);
  padding: 14px 22px;
  font-size: 12.5px;
  color: var(--fg-dimmer);
  text-align: center;
}

.footer a {
  color: var(--fg-dim);
  text-decoration: none;
}

.footer a:hover {
  color: var(--fg);
  text-decoration: underline;
}